Solvent extraction of Cr(III) from alkaline media with quaternary ammonium compounds. Part II

The extraction system, Cr(III)–NaOH–quaternary ammonium salt–hydrocarbon diluent–1-decanol, has been studied with respect to the loading capacity of organic phase, volume ratio of phases, and the effect of concentrations of some electrolytes in the aqueous phase. Trioctylmethylammonium chloride (TOMA-Cl) appears to be a much better extractant of Cr(III) from alkaline media than benzyldodecyldimethylammonium bromide (BDDMA-Br) because the loading capacity of organic phase with TOMA-Cl is over four times higher than with BDDMA-Br. The yield of Cr(III) extraction depends on the ionic strength of the aqueous phase and under optimal conditions does not depend on volume ratio of phases ranging from 0.1 to 1.0. The values of separation coefficient of Cr(III) and Al(III) reveal that these metals can be efficiently separated. Cr(III) is easily stripped from the organic phase with sulphuric acid solutions, and the organic phase regenerated with sulphuric acid can be successfully used for further Cr(III) extraction with the yield exceeding 99%. Under optimal conditions, recovery of Cr(III) with TOMA-Cl and/or BDDMA-Br from real industrial spent solution is practically complete.